The disclosure generally relates to an amplifier circuit and, more particularly, to the voltage adjusting circuit for the amplifier circuit.
The awareness of the energy depletion has drawn people's attention to the energy efficiency of the electronic devices. Moreover, as for smart phones, table computers and other portable devices, the users always care about how long the portable devices may operate before recharging. Improving energy efficiency may effectively prolong the battery time of the electronic device. There are various ways to improve the energy efficiency of the electronic devices, e.g., improving the energy efficiency of the amplifier circuit commonly adopted in the electronic devices.
The amplifier circuit is usually coupled between two fixed voltage level (e.g., the voltage levels of the power supply and the ground) for receiving power signals to generate the amplified output signal according to the input signal. Because the signal value of the input signal may vary dynamically, the signal value of the output signal varies accordingly and may not be bounded in a fixed range. To prevent the output signal from being bounded by the signal value(s) of the output signal(s) and resulting in the signal distortion of the output signal, the signal range of the output signal must be carefully configured in a suitable range between the coupled voltage levels.
If the signal range of the output signal is configured in a smaller range, the difference between the output signal and the power signal(s) is larger and the energy efficiency of the amplifier circuit is poor. If the signal range of the output signal is configured in a larger range, the difference between the output signal and the power signal(s) is smaller and the signal distortion of the output signal may easily occur when the signal value of the output signal varies. The system performance may therefore be influenced.
U.S. Pat. No. 7,830,209 disclosed a device and a method for adjusting the power signal transmitted to the amplifier circuit according the signal value of the output signal. However, when the impedance of the load of the amplifier circuit or the signal value of the power signal(s) vary, the signal distortion of the output signal and the energy efficiency still may not be effectively improved with the proposed solution.